I have a Vostro 220 connected via built-in network adaptor to a Netgear gigabit switch. When I first installed this switch I found it was still connecting at 100Mbps - Speed and Duplex was set to Auto Negociation. I selected 1.0Gbps Full Duplex and it did connect at 1Gbps.
I've recently noticed it's now connected at 100Mbps again even though still configured at 1.0 Gbps.
I've updated the driver via Windows 7 update - no change.
It is connected to the Netgear switch with a Cat 6 cable. Also connected to the switch is my WHS - at 1Gbps - and another Netgear gigabit switch, to which my other PC connects at 1Gbps.
Any suggestions would be welcome!